This invention relates to a spectrochemical analyzer of the type which utilizes colorimetric indicators responsive to specific chemical conditions. More specifically, this invention relates to spectrochemical analyzers which utilize optical means for determining the response of a color reagent to a change in a specific chemical condition.
The customary procedure for making a spectrochemical analysis using color reagents involves the use of a light transmission cell with the color reagent dissolved in the sample solution to be tested. By proper choice of the color reagents that method has been found to be highly specific and very sensitive and the apparatus involved is usually simple and relatively inexpensive. In the conventional approach to colorimetry, however, complicated sample preparations are frequently necessary. The conventional approach has the disadvantage of requiring that the color reagent be dissolved in the sample solution and therefore the color reagent be dissolved in the sample solution and therefore the color reagent is lost when the sample is discarded. Additionally, it is necessary that the concentration of the color reagent in the sample solution be controlled for consistent results. The conventional system also becomes difficult to apply in installations requiring long term, unattended, automatic operation and it is difficult to eliminate particulate interference, thus making it difficult to make measurements on sample solutions having any significant degree of opacity due to particulate matter. Also the conventional approach has problems with regards to calibration drift resulting from the gradual dirt deposition on cell windows.